Induced Charge Anisotropy: A Hidden Variable Affecting Ion Transport through Membranes

Improving solute selectivity is critical to enhancing the efficiency and sustainability of membrane separation processes. Doing so, however, requires understanding the molecular-level processes that culminate in solute transport through semipermeable membranes. Existing experimental techniques lack the spatiotemporal resolution necessary for probing such molecular-level events, and conventional simulation techniques cannot probe timescales relevant to the transport of unwanted solutes through ultra-selective membranes. Here, we use path-sampling molecular simulations to circumvent both these limitations. We not only accurately and efficiently compute arbitrarily long solute passage times but also identify induced charged anisotropy as a hidden variable affecting ion transport through nanopores. Our approach provides a scalable paradigm for computational studies of selectivity in applications such as desalination, chemical separation, and biological membrane transport.